Detection of psychophysical and structural injury in eyes with glaucomatous optic neuropathy and normal standard automated perimetry

Objective: To compare the prevalence of structural and psychophysical abnormalities in normal eyes and eyes with glaucomatous optic neuropathy (GON) and normal standard automated perimetry (SAP). Methods: Complete examination, SAP, short-wavelength automated perimetry (SWAP), frequency doubling technology (FDT), scanning laser polarimetry (GDx-VCC), and optical coherence tomography (OCT) of the peripapillary retinal nerve fiber layer (RNFL), optic disc, and macula were performed. Glaucomatous optic neuropathy was defined as cup-disc asymmetry between fellow eyes of greater than 0.2, rim thinning, notching, excavation, or RNFL defect. All eyes had normal SAP. Abnormal measurements on OCT, GDx-VCC, SWAP, and FDT were defined as those outside 95% normal limits. Eyes were stratified into 3 groups based on the OCT-generated vertical cup-disc ratio: mild, moderate, and advanced cupping (cup-disc ratio of < 0.4, 0.4-0.7, and > 0.7, respectively). Receiver operating characteristic curves were developed to assess sensitivity and specificity of structural and functional assessments. Results: Forty-seven eyes of 47 patients (25 with GON and 22 normal) were enrolled (mean +/- SD age, 58 +/- 16 years; range, 25-83 years). Compared with normal eyes, eyes with GON had significantly worse mean deviation and pattern standard deviation by means of SWAP and FDT (P=.02-.05); OCT-derived mean and superior and inferior RNFL thickness (P=.008, <.001, and .05, respectively); mean macular thickness (P=.01), rim volume, rim area, cup-disc ratio, and cup area (all P <.001); and GDx-VCC nerve fiber indicator and inferior average (P=.03). There was a significantly (P=.008, .002, .003, and .01, respectively) greater prevalence of abnormalities identified by SWAP, FDT, OCT and GDx-VCC in eyes with advanced cupping (43%, 43%, 57%, and 57%, respectively) compared with mild cupping (0%) and moderate cupping (9%, 5%, 19%, and 33%, respectively). Conclusions: Eyes with GON and normal results of SAP have significantly greater structural and psychophysical abnormalities than do normal eyes evaluated by means of OCT, GDx-VCC, SWAP, and FDT. Eyes with increased vertical cup-disc ratio are more likely to manifest such abnormalities on advanced diagnostic testing.